An integrated thermopile structure with high responsivity using any standard CMOS process

This paper reports a new thermopile structure using n-poly/p⁺ -active layers that are available in any CMOS technology. The thermopile structures are obtained by postetching of the fabricated and bonded chips. P⁺-active layers are placed in n-well regions, which are protected from etching by electrochemical etch-stop technique in a TMAH solution. The characterization results show that Seebeck coefficients of the n-poly and p⁺-active layers are -335 μV/K and 450 μV/K, respectively. Tests show that a cantilever type thermopile with 21 thermocouples will result in responsivity and detectivity of 43 V/W and 1.06×10⁷ (cm.√Hz)/W, respectively, when n-well is present and 617 V/W and 1.5×108 (cm.√Hz)/W, respectively, when n-well is removed